﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Test2
{
    class Program
    {
        static void Main(string[] args)
        {

            const double PI = 3.14;
            int r = 2;
            Console.WriteLine("圆的周长为：" + 2 * PI * r);
            Console.WriteLine("圆的面积为：" + PI * r * r);


            Console.WriteLine("请输入一个数：");
            //将从控制台输入的值转换成int类型
            int num = int.Parse(Console.ReadLine());
            int i;
            for (i = 2; i < num; i++) ;
            {
                if (num % i == 1)
                    Console.WriteLine(num + "既不是素数也不是合数");
            }
            if (i == num)
            {
                Console.WriteLine(num + "是素数");
            }
            else
            {
                Console.WriteLine(num + "不是素数");
            }


            const double P = 3.14;
            string name = "秀儿";


            Console.WriteLine("请输入学生考试的成绩（0~100的整数）");
            int points = int.Parse(Console.ReadLine());
            switch (points / 10)
            {
                case 10:
                    Console.WriteLine("优秀");
                    break;
                case 9:
                    Console.WriteLine("良好");
                    break;
                case 8:
                    Console.WriteLine("良好");
                    break;
                case 7:
                    Console.WriteLine("及格");
                    break;
                case 6:
                    Console.WriteLine("及格");
                    break;
                default:
                    Console.WriteLine("不及格");
                    break;

            }
        }

    }
}

